Phase corrector for telegraph systems



,Oct. 7, 1941. E. R. SHENK PHASE CORRECTOR FOR TELEGRAPH SYSTEMS 2 Sheets-Sheet 1 Filed March 30, 1940 Rm 3 Y 93 $7 W mwi INVENTOR. E06? R. SHEA/K ATTORNEY.

of transmission of telegrap January Mathes and of Clark the times of occ Patented Oct. 7,1941 v I UNITED STATE PHASE CORREC'I'OB a SYSTE Brooklyn, N. 1., asaignor to Eugene R. Shenk,

Radio Corporation of Delaware America, a corporation of Application March 30, 1940, No. 328,902

This invention relatesto improvements in a phase corrector for the distributor of a telegraph system. In order to maintain a receiving distributorin phase synchronism with the speed h signals, itfi's necessary that the signals shall produce a corrective action whenever tributor departs "from distributor. v

In phase correctors such as have been used in the past it has been common practice to obtain a corrective action by the use of the signal elements themselves in combination with locally be produced by derived pulses, such as may Usually means controlled by the distributor. such systems depended upon tween the front edge of a marking signal impulse and a locally derived impulse.

Improvements over the previously known and practiced methods of phase correction have been disclosed by Richard E. Mathes in his U. S. Patent No. 2,212,447, date application, Serial No. 316,458, which was filed 1940, by Gilbert R. Clark. The was assigned to the assignee In the systems of urrence of two local circuit closures are compared one with the front edge of a marking impulse and the other with the back'edge of such a marking impulse. Two distinct time intervals were therefore, derived, the durations of these intervals being differentiated from one another in such manner as to produce the necessary phase correction of a distributor.

The device disclosed in the instant application follows certain of the teachings ofMathes and of Clark, as above explained. However, I have found that the heretofore known systems may be made more dependable in their operating characteristics and the circuitarrangements are subject to simplification in a manner such as will be hereinafter set forth in more detail.

It is an object of my invention to provide a dependable circuit arrangement for correcting the phase of a telegraph distributor such as used in multiplex telegrap l. and to provide means for measuring two time tervals, one of which elapses between the fro t edge of a marking signal and a local impul near the normal cen-. ter of a time allotment for dot unit impulse reception, and to compare this time interval with another time'interval which starts from a moment near .the center of the unit signal Clark application of the instant application.

'1 Claims. (01.

the speed of the receiving disthat of the transmitting the relationship be"- marking signal.

It is another object of my invention to provide a phase correction system wherein use is made of a pulse wheel, rotatable integrallywith the distributor, for derivation of local impulses whose phase is to be compared with the phase of the incoming signals. 1

It is another object of my invention to pro- ''vide simplified circuit arrangements which eliminate the necessity for the use of certain filtering means heretofore thought to be essential.

It is still another object of my invention to provide a. phase correction circuit having output terminals which may be connected to any one of a number of different utilization devices, either for directly controlling the phase of a distributor d August 20, 1940, and in motor or for adjusting the frequency of an oscillator, such as may be used to maintain any desired telegraph apparatus in synchronism.

My invention will now be described in detail. reference being made to the accompanying drawings in which Figure 1 shows diagramma circuit arrangement including the essential elements in combination for carrying out the invention; and

Figs. 21 to 8 inclusive are plots of electric impulses which occur in various parts of the circuit arrangement. These plots are all drawn to the same horizontal time scale in order to show the correlation of essential operations in response to signals.

In the following description of a preferred embodiment of my invention all elements referenced VI, V2, V3, etc., will be understood to be discharge tubes, whether of the vacuum type V or of the gas-filled ionization discharge type. The gas-filled tubes, however, are conventionally designated'in Fig. 1 by means of. a black spot in the discharge zone.

Furthermore, the several resistors are refer enced RI, R2, R3, etc., while the several capacitors are referenced CI, C2, C3, etc. Specific reference to each of the tubes, resistors and capacitors will, for the sake of brevity, be frequently made by their identifying symbols alone. The two measured time intervals which are to be compared for purposes of phase correction of the distributor are obtained as follows:

The first or front end interval starts with the front edge of a marking signal impulse and terminates with the development of a local impulse designated P across resistor R26, this impulse time being derived from a magnetic pick-up coil 5,

allotment and terminates at the back edge of the tically a preferred whose pole pieces are positioned adjacent the orbit of a phonic wheel 3 having a suitable number of teeth therein, located in appropriate positions for producing a change of magnetic reluctance in the field of the coil 5. The phonic wheel 5 is mounted on the shaft with' the distributor whose phase is to be corrected.

The second time interval to be measured starts with a Q-pulse across resistor R1, as developed in a pick-up coil 1 whose pole pieces are positioned adjacent the orbit of the teeth in the phonic wheel 6. The termination of this back end time interval is produced at the .back edge of a marking'signal impulse.

One or both of the pick-up coils 5 and I may 326,903, filed March 30, 1940. 'In the respective cases, however, the oscillator is claimed only as an element in combination with features by which the two disclosures are patentably distinguished. I will now explain how the incoming signals and the locally derived impulses from the pickthrough transformer T and rectified by a full be oriented about the axis of the phonic wheel 6 so as to cause these impulses to be generated, one immediately before and the other immediately after the normal center of reception of a marking impulse of dot unit length.

As will be hereinafter shown, the front end integration period is represented by a charge stored on condenser 014, while the back end integration period is correspondingly represented by a charge stored on condenser C5. These charges are held until a space occurs following a marking impulse. If, however, the marking impulse is of longer duration than one clot or band, the successive charges stored on condenser C5 are wiped out until the last one preceding a spacing signal, so that, regardless of the length of the marking signal, there is always a comparison to be made between the effective charges on C and C5 suitable for purposes of applying correction to the receiving distributor.

Differentiation between the charges on GM and C5 respectivelyis manifested by means of two triode tubes VH and VI5 arranged in a differential circuit relationship, their anodes being interconnected through a. resistive circuit at the center of which direct current from a +3 source is applied. The relative conductivity across the space paths of VI4 and VI5 determines the potential drop across R38, R39 and R40 in relation to that across R4l, R42 and R43.

Since, however, R40 and R43 constitute bias resistors in the input circuit of a discharge tube V20, said input circuit including an independent grid biasing source 5|, it will be seen that this triode tube V is in position to be controlled by the sense of polarity of the potential drop across these resistors R40 and R43.

The tubes VI4 and VI5 are rendered conductive only during spacing intervals and the amount of current flowing in each is determined by the charges respectively stored in capacitors CM and C5. Hence the anode circuits .of W4 and VI5, will carry comparable currents through the resistors R40 and R43, such as may be utilized in any preferred device or circuit arrangement for maintaining synchronism of the receiving apparatus with respect to the incoming signals. Such a synchronizing device may, for example, be in accordance with the disclosure of Clark in his aforementioned application, wherein a threeposition relay was used. The double winding of that relay was disposed correspondingly to the resistors R40 and R43 as herein shown in Fig. 1.

Alternatively the synchronizing device may include an oscillator whose frequency is controlled by a reactor, the value of which depends on the differential between the currents in the output circuits of the tubes V14 and VI5. A suitable oscillator circuit of that type is disclosed herein, as well as in my copending application Serial No.

- pears across RM, to the control grid of electron up coils 5 and 1 maybe made effective to store charges on the condensers CH and C5, so that the proper control of the tubes VH and VI5 may be obtained.

The received multiplex signal consisting of a tone for mark and no tone for space is passed wave rectifier tube VI. A diagram of the signal input before rectification is shown in Fig. 2.

The rectified signal voltageappears across resistor R" in the polarity indicated, that is, with the positive end connected to'ground.

The negative signal voltage is applied, together with a threshold determining voltage which apdischarge tube V2, thereby shifting this grid from a normal zero bias to a cut-off bias. V2 is, therefore, blocked for the duration of the marking signal.

A connection is also provided from a mid-tap on the secondary of transformer T to a potentiometer R29, and thence through resistors R28 and R30 to the grids of tubes VM and VI5. The potentiometer R29 is connected at one end to a source of biasing potential, -C, more negative than ground. Normally, therefore, there is a potential gradient across the potentiometer R29 from its 0 terminal to its other terminal and thence through RI I to ground. This potential gradient is, therefore, available as a biasing potential on the grids of tubes V and VI5. The tubes VM and VI5 are, therefore, controlled only during spacing intervals and when they receive a positive bias across resistors R28 and R30 respectively, as derived from the discharging of condensers CH and C5, as will be hereinafter explained. V and VI5 are, however, main tained at cut-off bias during each marking interval by virtue of the rectified negative potential at the center tap of the secondary winding on transformer T which is additive with the above mentioned C potential.

The control of V2 by the negative signal voltage is such as to biasthis tube to cut-off and hence to raise its anode potential to the full +B voltage.

A positive impulse is, therefore, impressed across C9 which produces a potential drop in R25. This impulse is reflected into a circuit leading to the grids of two gaseous discharge tubes V4 and VIZ for igniting the same at the front edge of a marking impulse. The discharge in Vl2 is only momentary and serves to dissipate any residual charge on GM down to a reference voltage, at which Vl2 becomes automatically extinguished.

When the gaseous tube V4 strikes, an impulse is impressed across Cll which lowers the potential on the anode of V6 momentarily, and to such a value as to extinguish this tube. V4 and V3, because of their intercoupled anodes, are said to be in back-to-back relation to one another. Condenser Cll is then quickly charged positive on the side of the tube V6. Cl4 charges through attem- V3 rises to +3 voltage, a positive P-pulse is impressed across 08 and R20, the latter being in circuit between the C terminal of a biasing source and the grids of V and V1. Disregarding V1 for the moment, the positive impulse causes V6 to strike. At this moment V0 extinguishes V4, since C is now momentarily charged in the reverse direction from. formerly. The re duced voltage on the anode of V0 terminatesthe current flow through VIO, since the cathode thereof is now positively polarized by CM and is more positive than the anode of V0. VII, therefore, serves to isolate the charge on C and to store the same until it can be utilized for comparisonpurposes during a space interval following a marking period.

At the commencement tegration period a Q-pulse is delivered by the impulse coil 1. The moment when this takes place is slightly delayed after the normal center of a baud has been reached. This delay is equal to the anticipitation period of the P-pulse in advance of the baud center. the Q-pulse effective only during marking periods I provide a vacuum discharge tube V8 having an of the back end in- 1' 8. 8. are indicated-in Fig. ."l, where the Q-pulse is followedby the termination of the marking signal as denoted by the'occurrence of an S- pulse. This is distinguished i'romi P-pulse because it occurs at a dlflerent timejand in response to the commencement of the conductive period of V2, that is, at the commencement of a spacing, period.

V2, when its anode voltage is reduced in response to-the cessation of the rectified signal voltage, momentarily biases VI to cut-ofl, The

in responselzo a P-pulse from thepick-up coil 5.

It will beseen from the above, and from a comparison of Figs. 2 to 8 inclusive, that the various pulses designated M,P, Q and S are caused to control the charging times on C5 and C in such manner that these charges may be differentiated during a spacing interval. The charge stored on Oil represents the front end integration I period, while the charge stored on C5 represents In order to render input circuit which includes RI and a junction" point between RN and Rl0,and thence through Rl8 and R" to ground. The Junction point between Rl8 and RI! is alsoconnected through RIB and R20 to the +B terminal and is afiected by the rectified signal voltage. Consequently V8 which normally draws current through R2 is biased to cut-off by and during a marking signal. It is only at such times that V9 is supplied with sufficient anode potential to amplify Q-pulse from the pick-up coil 1.

V9 is operating at zero bias and. when it receives a negative pulse from the pick-up coil 1 this pulse is delivered positively after amplification across C2 and develops a voltage across R'l connected between the -C terminal and bias resistor R6 leading to the grid of a gaseous tube V5. In shunt with R6 and the grid of V5 is a grid resistor RH! and the grid of a gaseous tube V13.

V5 and W3 are both ignited by a Q-pulse. The

discharge in Vl3, however, lasts only until it can dissipate a residual charge on C5 and reduce the voltage thereof to a reference point at which Vi3 becomes automatically extinguished When V5 strikes, C4 momentarily reduces the anode voltage on V1 to a point where this tube is extinguished. Immediately therefore the anode of V1 rises to full +B voltage and C5 starts to charge by virtue of the conductivity of Vi I which is a diode rectifier. This charging current flows through R9, RH and VI I.

In case the marking impulse is of dot unit length, or one baud, the charge stored on C5, as above described, will be effective immediately upon the termination of a marking impulse and will produce a discharge in Vi5 commensurate with and representing the back end integration period. If, however, the marking impulse is of longer duration, then it is necessary to suecessively wipe out the charge on C5 by a P-pulse and. to resume charging the same in response toa Q-pulse. V1 is ignited by a P-pulse. At that moment V5 becomes extinguished and is prepared to receive asucceeding Q-pulse. The in effective charging times of C5 are'indicated in the back endintegration period.

The spacing signal itself, as has heretofore been shown, changes the bias onthe grids of V and VI! so that the'voltages of the condensers CM and C5 may control the conductivity of these tubes difierentially.

It is known in the art .that a multiplex distributor may-be phase-controlled by a vacuum tube oscillator. disclosed in United States Patent No. 1,747,248, granted February 18, 1930, to W. A. Knoop.

Other systems of speed control and phase correccuits for the two .tubcs VM and VIE. This voltage is impressed across R40, R39 and R38 to the anode of V. The +B voltage is also impressed across R43, R42 and R to the anode of VI5. In order to smooth out the action of the tubes capacitor .Cl5 is connected between the +3" terminal and the junction between R38 and R39. A capacitor C I 6 is similarly disposed between the +3 terminal and the junction between R and R42. An amplifier tube V20 has an input circuit which includes its control grid, resistors R40 and R43, and an independent source 5! of C- potential, whose positive terminal is connected to the cathode of V20.- V20 requires also an in-,

whose input circuit includes a resonant unit may, therefore, be understood, this control being impressed across capacitor C2l., The resonant circuit is indicated at 22, one end of which is The charging times, however,

For example, such a system is grounded, the other end being connected to the grid of an oscillator tube V23.

Because V23 is self-biased there will be no bias when the circuit is first turned on. Therefore, a pulse of plate current will flow in V23. This pulse is fed to V25 which amplifies and limits This amplified, inverted change of current in V23 and the cycle is repeated.

The oscillator V23 has a grid-to-cathode circuit which includes potentiometer 54 and a resistor 55. Capacitor 55 is in shunt with resistor 55. Amplifier tube V24 has its cathode connected to the cathode of V23. V24 possesses a control grid circuit which includes a tap on potentiometer 54. V24 is, therefore, controlled in phase with V23 and its output power may be adjusted to any desired value by means of the adjustable tap on potentiometer 54. The output circuit of V24 includes the primary of a transformer 52 and an anode potential source which is common to the output circuit of V25. The secondary of transformer 52 delivers a controlled output frequency which; is suitable for distributor phase correction purposes.

I claim: 1. A system for synchronizing a telegraph dis tributor with a train of incoming marking signal comprising means for producing in the following sequence four species of control pulses M, P, Q and S, of which M and S are responses to the arrival of the front and back edges respectively of each marking signal, and P and Q are timed to occur at equal intervals before and after a reference phase of said distributor, electrical means for differentiating between the duration of M-to-P intervals and Q-to-S intervals,'an oscillator having frequency control means subject to the influence of said differentiating means, and means for causing said oscillator to correct the phase of said distributor.

2. A system according to claim 1 in which said differentiating means comprises a capacitor receptive of a charge proportionate to the M-to-P interval and a second capacitor receptive of a charge proportionate to the Q-to-S interval, a pair of vacuum discharge tubes and means operative during a spacing period for subjecting one of said tubes to the control voltage of the first said capacitor and for subjecting the second of said tubes to the control voltage of the second said capacitor.

3. In a synchronous telegragh system for the reception of keyed signals the marking elements of which are of baud length and multiples thereof, means including two capacitors for accumulating comparable charges, pulse generating means for so timing the occurrence and duration of said charges that one commences at the front edge of a marking element and terminates prior to the arrival of the next succeeding baud center, and the second of said charges commences after the arrival of a band center next preceding the back edge of said marking element and terminates on arrival of said back edge, means for storing said charges, means operative during the next succeeding spacing element of the signals for differentiating between the values of said charges,

a distributor, means including an electron discharge tube oscillator for controlling the phase of said distributor, and means for causing the frequency-of said oscillator to be varied in occordance with the differentiation between said charges.

'4. In a phase corrector for a receiving telegraph distributor, a magnetic pulse wheel rotatable with the rotor of said distributor, a pair of pick-up coils each arranged to generate a periodic succession of impulses in fixed synchronous relation to the rotation of said pulse wheel, means responsive to the reception of the front edge of a marking signal element for initiating an ionization discharge, means responsive to the next succeeding impulse from one of said pick-up coils for extinguishing said ionization discharge, a capacitor for storing a charge substantially proportional to the duration of said ionization discharge, means responsive to an impulse from the second of said pick-up coils for initiating a second ionization discharge, means responsive to the reception of the back edge of said marking signal for extinguishing said second ionization discharge, a second capacitor for storing a charge substantially proportional to the duration of said second ionization discharge, means operative during a spacing signal for comparing the voltages of the two charges thus stored, an oscillator for controlling the speed of said distributor, and means operative in accordance with the magnitude and sense of the voltage difference between said two charges for synchronizing said oscillator and the distributor with the incoming signals.

5. A phase corrector in accordance with claim 4 and including means for discharging each of said two capacitors downv to a predetermined reference voltage prior to the accomula-tion thereon of the charges to be compared.

6. A phase corrector in accordance with claim 4 and including means to nullify the effects of storing charges on the second capacitor when accumulated during a relatively long marking period and prior to the generation by said second pick-up coil of an. impulse which next precedes the arrival of the back edge of the marking impulse.

7. In combination, a source of two synchronizing impulses, one being effective on the arrival of the front edge of a marking signal, the second being effective on the arrival of the back edge of said marking signal, a periodic device having means controlled thereby for delivering two local pulses, one in advance of and the other equally in arrears of the baud center as determined by said periodic device, means including two separate capacitors for storing charges thereon which represent two time periods to be differentiated, one of said periods extending from the front edge of a marking impulse to the next succeeding local pulse, the other of said periods extending backwards from the back edge of said marking impulse to the next preceding local pulse, an oscillator, having a frequency-determining element in its input circuit, and means under control of currents derived from the differentiation of said stored charges for so adjusting the value of said frequency determining element as to effect synchronization of said periodic device with said signals.

EUGENE R. SHENK. 

